1. Field of the Invention
The present invention pertains to a device for transferring thin plate substrates, glass substrates, etc. (hereinafter referred to as "wafers" generically), and more particularly to a device for transferring wafers to be treated to and transporting treated wafers from a holding member. The holding member holds the wafers one at a time, receives them consecutively and operates in the manner of a rotary circular vacuum chuck member found in a treating part of a variety of types of apparatuses for treating the wafers while rotating the same, and as a susceptor in a lamp annealing apparatus, and the like.
2. Description of the Prior Art
A wafer transferring device is described in Japanese Patent Application Kokai No. 53-73372 (Kokai No. 54-163933). FIG. 11 herein is a schematic vertical sectional view illustrating a conventional apparatus for supplying a water W1 to be treated to a rotary circular vacuum chuck member 103 and carrying away a treated wafer W2 simply by horizontally reciprocating just one time a wafer transfer unit 104 between a start position adjacent to a supply belt conveyor member 101 and a discharge belt conveyor member 102.
Care is taken to assure that the level of the wafer conveying surface of the member 101 is higher than that of the wafer holding surface of the member 103, while the surface of the member 103 is higher than that of the wafer surface of the member 102. Furthermore, the level of an untreated wafer placing part 104a of the unit 104 is lower than that of the upper surface of the member 101, whereas it is higher than that of the surface of the member 103. On the other hand, the level of a treated wafer placing part 104b of the unit 104 is lower than that of the surface of the member 103, while it is higher than that of the surface of the member 102. The unit 104 travels along a rail 105 horizontally from the left to right parallel to the plane of FIG. 11 upon receiving on its untreated wafer placing part 104a the wafer W1 being projectingly handed over from the member 101. When passing the chuck member 103, the unit 104 receives the treated wafer W2, on its treated wafer placing part 104b, by bumping the rear edge, as viewed in the above direction, of the wafer W2 at a step 104c thereof defined by adjoining portions of the parts 104a and 104b in different heights. When the unit 104 reaches the discharge conveyor member 102, a pin 107 jumps up to contact the aforesaid edge of the wafer W2, and then the transferring unit 104 is returned to the start position with the wafer W2 being deterred by the pin 107 from being drawn by the returning unit 104, thereby permitting the wafer W2 to remain on the discharge conveyor member 102. Thus, the transfer of the wafer W2 onto the member 102 from the unit 104 is effected.
During the transferring operation, as unit 104 is returned to the start position, a detent piece 106 rises up and makes contact with the front edge, as viewed in the right to left direction parallel to the plane of the drawing, of the wafer W1 at the time the unit 104 passes the chuck member 103, so that the wafer W1 on the part 104a is transferred onto the chuck member 103.
In this type of the device, however, certain problems remain. The transfer of the treated and untreated wafers W2 and W1 onto the discharge conveyor member 102 and onto the vacuum chuck member 103 from transferring unit 104 is effected by moving the member 103 toward the supply conveyor member 101 while preventing the wafers from moving horizontaly along with the unit 104 by means of the pin 107 and the detent piece 106. This causes the lower surfaces of the wafers to rub against the upper surfaces of the parts 104b and 104a. Consequently, the surfaces of the wafers W1 and W2 are minutely impaired and soiled by the prior art's transfer mechanism.
Furthermore, the transfer of the wafer W2 from the chuck member 103 onto the part 104b of the unit 104 is effected by causing the left-wise moving step 104c of the unit 104 to bump/push forward the rear edge of the wafer W2. Consequently, the lower surface of the wafer W2 is forced to rub against the upper surface of the member 103, thereby creating fine scratches in and staining the lower surface of the wafer.